This invention relates to methods of water proofing inorganic surfaces with an aqueous solution containing an ionic organosilicon compound. Additionally, the present invention is directed to an inorganic surface treated with an aqueous solution containing an ionic organosilicon compound such that a water resistant film covers the inorganic surface.
Water resistance is an important issue in many types of construction including masonry and concrete. Resistance to water is of great importance since moisture absorption and its movement in these types of materials cause or contributes to problems such as expansion, shrinkage, cracking, staining, mildew, lowered resistance to freezing and thawing, chemical attack, corrosion of reinforcing steel, and damage to structures from settling. Due to these problems, various techniques have been used to render these types of surfaces water resistant including surface treatment of structures with water repellents. Water repellents that have been used in the past include oils, waxes, soaps, and resins. These repellants have been applied to surfaces by brush, roller, air spray, or airless spray techniques. One type of water repellent that has been used is organosilicon compounds. These compounds in organic solvents have been found to be useful for providing water resistance to brick, concrete, stucco, or terrazo surfaces.
As discussed in U.S. Pat. No. 5,073,195, the contents of which are hereby incorporated by reference, application of organosilicon compounds to surfaces for water proofing is well known in the art. The use of organosilicones such as alkyltrialkoxy compounds for imparting water resistance has been known for at least 30 years. Traditionally, application of these compounds was carried out in flammable solvents such as ethanol, methanol and various liquid hydrocarbons. During application, volatile organic compounds (VOC) were heavily emitted. Due to these problems, significant efforts were employed to formulate a nonflammable composition for imparting water resistance to masonry and concrete surfaces. The first approach attempted included various water emulsions containing organosilicon compounds. However, these formulations failed to provide water resistance comparable to the solvent based compositions. In recognition of the shortcomings associated with the water emulsion formulation, formulations were developed to make alkyltrialkoxy silanes water soluble. Formulations of this type utilize water soluble amino and quaternary ammonium organosilanes along with alkyltrialkoxysilanes of the traditional formulations. The intent of these formulations was to exploit the soluble organosilanes to solubilize the alkyltrialkoxysilanes, which provided the water repellant characteristic.
In addition to water resistance, numerous types of construction materials benefit from treatment with an antimicrobial agent. Antimicrobial agents are chemical compositions that prevent microbial contamination and deterioration of materials. Possibly the most prevalent group of antimicrobials is quaternary ammonium compounds. The use of low level (1% or lower) quaternary ammonium silanes as antimicrobial agents is well known and taught in a wide variety of United States patents including U.S. Pat. Nos. 3,560,385; 3,794,736; and 3,814,739. Due to their antimicrobial qualities, their application is beneficial for a variety of surfaces, substrates, instruments and applications. Examples of such uses are described in U.S. Pat. Nos. 3,730,701; 3,794,736; 3,860,709; 4,282,366; 4,504,541; 4,615,937; 4,692,374; 4,408,996; and 4,414,268; the contents of which are hereby incorporated by reference. Application of an aqueous solution containing a quaternary ammonium silane is discussed in U.S. Pat. Nos. 4,921,701 and 5,169,625.
Relevant to the present invention are U.S. Pat. Nos. 5,209,775, 5,421,866, 5,695,551, CA 2,115,622 and JP 3,159,975. These patents are directed to water dispersible or water emulsion water repellent compositions of silicon compounds. The compositions disclosed in these patents contain (1) alkylalkoxy silane or siloxanes; (2) a water soluble silane; and (3) either aminosilane or quaternary ammonium silane. The role of soluble silane, aminosilane or ionic quaternary ammonium silane, in these compositions is to stabilize the alkylalkoxysilane, siloxane, or other water insoluble polymers in water.
The use of hydrophobic water insoluble silanes as water repellents in various organic solvents such as alcohols and hydrocarbons has been traditionally preferred due to their superior performance. However, the principal limitations of these solvent type compositions include their inherent toxicity and flammability. While providing an ecological improvement over solvent based treatments, the existing organosiloxane emulsions and water dispersible silanes or siloxanes do not compare well with existing solvent-base silanes, silane/siloxanes combinations or siloxanes in terms of stability, penetration depth, and the beading effect of the treated substrate. Additionally, the use of surfactants may cause rewetting of the surface.
Therefore, there remains a need for an aqueous water proofing treatment capable of providing at least equally efficient water resistance as treatments utilizing solvent based compositions. Accordingly, it is an object of the present invention to provide a method of treating surfaces with an aqueous solution; wherein the treated surface exhibits water resistance at least equal to that provided by solvent based treatments. Additionally, it is an object of this invention to provide the following three highly desired requirements for providing long term hydrophobicity on inorganic substrates: (1) application of a safer and environmentally acceptable aqueous solution, (2) imparting molecular level hydrophobicity and (3) reactivity with a substrate to provide long term performance.